Communication system and device using dynamic receiver addressing

ABSTRACT

Method and a system for establishing a communication channel between a first communication device, or alternatively, a communication network operator, and one or more second communication devices. The identity of the one or more second communication devices is not pre-determined by the first communication device (or the communication network operator). Instead, the identity of which one or more of the second communication devices connects to the first communication device (or the network operator) is determined by the operation of one or more filters transmitted by the first communication device (or the network operator) on certain data that are both transmitted by the first communication device (or the network operator) as well as measured locally at each of the second communication devices.

This application is a divisional of U.S. patent application No.08/920,512, now U.S. Pat. No. 6,115,605, filed Aug. 29, 1997, which isincorporated herein by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to telecommunications, and morespecifically to wireless messaging systems.

In connection with communication systems, especially radiotelephone andpaging systems, it is well known that the identity and/or functionalityof particular subscriber receiver units with whom a calling party or thecommunication network operator wishes to establish a communicationchannel is either predetermined and fixed, or can be selected a priorieither by the calling party, the communication network operator, or theparticular subscriber themselves. By a priori it is implied that theselection is done prior to reception of data by the particularsubscriber receiver units.

FIG. 1 depicts the high level operation of a typical prior artcommunication network. In the figure, a first device originates arequest for establishing communication with any one or several of secondcommunication devices. The first device connected to the communicationnetwork either via the internet or via a regular Plain Old TelephoneSystem (POTS). Of course, other connecting technologies may also be usedfor connecting the first communication device to the communicationnetwork. The message from the first communication device is packaged andtransmitted by the communication network operator to several secondcommunication devices through localized Towers or Base Stations orExchanges (nomenclature well recognized by one skilled in the art). Onlya subset of the several second communication devices recognizes itsaddress embedded in the transmitted message and consequently only thissubset receives the transmitted message.

FIG. 2 depicts the operation of a prior art second communication deviceused in conjunction with the existing communication network depicted inFIG. 1. The transmitted signal contains an identification tag, labeledTransmitted ID in the figure, indicating which one or several of thesecond communication devices are to process the accompanying messagedata. The box labeled Front End in the figure encapsulates all thecircuitry in the device required for interfacing the device with thecommunication network and extracting the contents of the transmittedsignal (i.e., Transmitted ID and Message). The Transmitted ID is checkedfor equivalence with a locally stored ID and if there is a match (i.e.,the two are equal), the accompanying Message data is further processedto result in some appropriate action (e.g., display of message,generation of tone, etc.). If there is no match the Message data isdiscarded and the receiver simply ignores the incoming transmittedsignal.

For ease of understanding, the block diagram of the communication devicein FIG. 2 is divided into three different spaces: Data Space, FilterSpace, and Action Space. The Data Space in FIG. 2 simply consists of oneor several pre-defined numerical values (referred to here as ID values)using which the particular device can be identified. These ID values maybe unique or shared with other devices; however, in all cases they arepredetermined before transmission of data to the device. The FilterSpace is responsible for checking equality between Transmitted ID andlocal ID and generating a True/False answer. In essence the output ofthe Filter Space determines whether or not the Transmitted Message wasintended for reception by the communication device. The Action Space isthe result of processing of the received message in the event FilterSpace returns True, else it is null, i.e., there is no action.

SUMMARY OF THE INVENTION

The invention relates to a method and a system for establishing acommunication channel between a first communication device, oralternatively, a communication network operator, and one or more secondcommunication devices. The identity of the one or more secondcommunication devices is not pre-determined by the first communicationdevice (or the communication network operator). Instead, in certainembodiments the identity of which one or more of the secondcommunication devices connects to the first communication device (or thenetwork operator) is determined by the operation of one or more filterstransmitted by the first communication device (or the network operator)on certain data. The data may be transmitted by the first communicationdevice (or the network operator) as well as measured locally at each ofthe second communication devices.

By virtue of the fact that the nature of the transmitted filter, thevalue of transmitted data, and the value of locally measured data isvariable, i.e., can change with time, the identity of the same secondcommunication device itself can change with time. Further, since thevalue of locally measured data is typically not determinable by thefirst communication device, the first communication device cannotdetermine the identity of second communication device a priori.

A further aspect of this invention relates to the fact that acommunication channel established between the originating communicationdevice that makes a request and one or more selected communicationdevices, each connected to an entity that can service the request,includes a feedback loop that enables the requesting device tocontinuously receive status updates of the servicing entities throughtheir respective communication devices. Selection of the calledcommunication devices may or may not be dynamically determined.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representative prior art communication system;

FIG. 2 shows the operation of a communication device in conjunction withthe prior art communication system depicted in FIG. 1;

FIG. 3 shows the operation of a communication device that is used inconjunction with a communication system embodying the invention;

FIG. 4 shows a specific embodiment of the communication device of FIG.3;

FIG. 5 shows a communication system having a feedback loop according toan embodiment of the invention;

FIG. 6 is a table illustrating design considerations relating toproviding capabilities in the mobile device and the network;

FIG. 7 is a detailed block diagram of an embodiment of the communicationdevice; and

FIG. 8 is a detailed block diagram of an embodiment of the serviceoperator.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention embodies a scheme that significantly enhances thevalue of currently deployed communication networks by increasing theintelligence of the attached communication devices as well as enrichingthe message protocol between the various communication devices and thecommunication network to take advantage of the enhanced intelligence inthe communication devices. The present invention provides moreflexibility to the users of the communication network and the networkoperator by allowing the identity of the attached communication devicesto vary, possibly in a non-deterministic manner. (In the context of thisinvention the word “identity” implies a measure that is used todetermine whether or not a communication device is the one that isintended for reception of a transmitted message. More than one devicemay share the same identity.) Furthermore, the nature of variance of theidentity of any particular communication device is not required to beknown a priori to any device, user, or the network operator. Rather, theactual identity of a particular device is computed using informationcontained in the transmitted signal and certain other dynamicallyvarying parameters that are only locally available at the device, andfurthermore, only at the instant that the identity is computed is itknown to that device as to whether or not the transmitted signal wasintended for reception by it.

This is in contrast with existing prior art communication networks,especially radiotelephone and paging networks, wherein the identity ofany communication device attached to the network is known prior totransmission of any message intended to be processed by saidcommunication device. In certain prior art communication networks, suchas television and radio broadcast networks, the sender is not requiredto know the identity of any receiver unit prior to transmission of data.However, in these networks, the receiving entity needs to know, apriori, which data it is desirous of receiving before it can receivethat data. Reception of desired data is then accomplished by “tuning”the receiver to a predetermined mode that is compatible with thetransmission format of the desired data.

There are several possible situations, especially when the originatorand receiver of information are physically separated, when it is notknown a priori as to whether or not a certain receiver requires theinformation. This is because generally the conditions under which thereceiver requires information depend on certain locally varyingparameters, such as geographic location, temperature, direction ofmotion, etc., depending on the application, as well as certain otherconditions that are set by the originator of the communication.

For example, in a certain application the originator of the informationmay want to communicate a particular emergency message to all mobilereceiver units that are currently located in a specific geographicregion (say within a pre-specified radius of an accident). Whichreceiver units are eligible to receive the particular emergency signalcan only be determined at the instant the communication has to occur,since the movements of all the mobile receiver units are unknown to thesender of the signal. Additionally, even though each receiver unit mayknow in advance its exact movements, it cannot anticipate at whatinstant a message is going to originate from the sender, as well as whatgeographic constraints are embedded in it. Consequently, it cannotchoose a priori the type of message it wants to receive. Furthermore, ifa particular receiver unit moves outside the specified geographic zone,it is no longer eligible to receive the same message, even though thetransmitted signal “may still be visible to it”; in other words, afterleaving the specified geographic zone, it assumes a different identitywith respect to the said message. Prior art communication receivers andnetworks do not readily support implementation of such a flexiblecommunication paradigm.

FIG. 3 depicts the operation of a communication device when it is usedin conjunction with a communication network that supports the schemeembodied in the present invention. The differences between the diagramsin FIG. 3 and FIG. 2 are related to the information contained in theTransmitted signal, the Data Space, and the Filter Space.

The Transmitted ID field of the transmitted signal in the presentinvention is significantly enhanced as compared to prior art systems toinclude additional data along with one or more “filters”. A filter, inthe context of this invention, is simply an algorithm or a rule thatwhen applied to certain data results in a True/False answer.

Prior art communication networks also employ a filter, albeit adegenerate “equality” filter, that simply verifies equality between twonumbers. This was illustrated in FIG. 2. Furthermore, the filterdefinition in prior art implementations is fixed and not alterable oncethe communication device is deployed. For this reason the definition ofthe filter is not required to be transmitted in prior art communicationssince every communication device already knows it. Only the data istransmitted and this has been referred to in FIG. 2 as Transmitted ID.

The actual specification of filters in the transmitted signal of thepresent invention is a matter of implementation. In certain networks,where it is desired that the implementation be simple, the networkoperator and all communication devices agree a priori to a certain setof applicable filter definitions. Each one of these filter definitionsis assigned a unique code and the mapping between filter definition andcode is stored in non-volatile memory in every communication device. Thecommunication network also has a copy of this mapping available to it.Whenever a particular filter definition is required to be transmitted,its corresponding code (along with any required data) is transmittedinstead. All receiving communication devices and the network canregenerate the filter definition from their local copy of the mapping.In certain other networks, where it is desired to have significantsophistication, entire definitions of filters are transmitted. Thedefinitions are in the form of object code that can be executed in allcommunication devices. Alternatively, the definitions may be in the formof a platform-independent language, such as Java. In this case eachcommunication device is equipped with an appropriate interpreter (suchas a Java interpreter) using which it can convert the filter definitioninto an executable set of commands.

Another feature of the invention relates to the Data Space over whichthe filter operates. In prior art communication devices the Data Spaceconsists of one or several pre-determined numerical values, which areused to specify the identity of the communication device. The FilterSpace operation consists of verifying equality between any one of thesevalues and the Transmitted ID value. In this invention, the Data Spacecan be significantly expanded to include not only stored, pre-determinedvalues, but also values that are dynamically generated throughmeasurement of one or more localized parameters. For example, in oneembodiment, the localized parameter is the geographic location of thecommunication device, as measured or indicated by a GPS receiver that isconnected locally to the communication device. In another embodiment,the localized parameter is a temperature value that is input to thecommunication device from a temperature sensor connected to it. In yetanother embodiment, the localized value is an indicator of currentinventory status of certain merchandise that is being monitored by theuser of the communication device. These are but illustrations ofquantifiable parameters whose value is being input to the communicationdevice. The important point is that the locally generated value is notnecessarily fixed and unvarying; rather, it can vary with time dependingon the local conditions surrounding the communication device.

The locally generated parameter values can be entered into thecommunication device either on a continual basis, or they may be sampledat discrete time instants. This is a matter of implementation and isdependent on the particular application.

Another feature of the invention relates to the Filter Space. Asmentioned previously, the Filter Space in prior art implementationconsists of the operation of checking equality between the TransmittedID and one or more of locally stored ID values in the device's DataSpace. In the present invention the Filter Space is expanded to imply ageneralized filter operation on data carried as part of the Transmittedsignal, as well as the dynamically varying data available from thecommunication device's Data Space. The filters used for the operationmay be either stored in the communication device's non-volatile memory,or they may be downloaded from the received signal, as described above.The result(s) obtained from the filter(s) operations is(are) used todetermine if the Transmitted Message is intended to be received by thecommunication device. In other words, the result(s) determine theidentity of the communication device with respect to said TransmittedMessage.

An important consequence of including dynamically varying local data inthe Data Space is that the result of applying the transmitted filter tothe data can no longer be predicted in advance by the communicationdevice, its user, or the network. Since the purpose of applying thefilter is to determine whether or not a particular communication deviceis eligible to receive the message, it is quite possible that the samedevice may or may not be found eligible to receive a particular messagebased on the available data in its Data Space. In other words, theidentity of any communication device is no longer fixed, but isdynamically determined by its local conditions.

FIG. 4 shows a specific embodiment of the device described withreference to FIG. 3. The unit depicted in FIG. 4 contains a GlobalPositioning Satellite (GPS) receiver, a communication transceiver suitedto the appropriate network the unit is designed for, and amicro-controller. The function of the Data Space portion of thegeneralized module described in FIG. 3 is fulfilled by the GPS receiver.The purpose of the GPS receiver is to monitor the signals available fromthe GPS satellites and determine the location of the unit. This schemeis well established and known to those skilled in the art. The currentlocation of the unit, i.e., latitude, longitude and altitude, is thelocal data on which the downloaded filter operates. The function of thecommunication transceiver sub-system in FIG. 4 is to provideconnectivity to the external network.

The Filter Space of the unit in FIG. 4 is implemented as software insidethe host micro-controller. For example, in a specific application, thedefinition of the downloaded filter may be: “return true if currentlocation is within a pre-specified distance of a pre-specifiedlocation.” In other words, executing the filter involves determining ifthe distance between the pre-specified (i.e., downloaded) location andthe unit's current location is smaller than the pre-specified (i.e.,downloaded) distance value. This can be done inside themicro-controller; the result is also interpreted by the software in themicro-controller using which it determines the actions to be taken. TheAction Space in FIG. 4 is represented by the user interface arrow (“userI/F”), which is controlled by the host micro-controller.

It can be appreciated by those skilled in the art that implementing theFilter Space as software renders it relatively simple to change thefilter definition. For example, the definition of the filter in theprevious paragraph can be easily altered to imply a different distancecalculation. The same unit that responds to the first filter with a truecondition may respond to the second filter with a false condition. Inother words, the identity of the unit changes with the definition of thefilter, as has already been explained above.

FIG. 5 illustrates a further aspect of this invention. This aspectrelates to applications involving situations in which an entity requestsa service from a remote location. The request is made through existingbi-directional communication networks that allow the service operator tocommunicate back with the requester. However, the service beingrequested itself is of such nature that it requires physical movement ofone or more entities from a remote location to the requester, anactivity that cannot be performed using the communication network overwhich the request is made. (In contrast, an example of an applicationwherein the requestor is serviced over the same network as the one onwhich the request is made is downloading of data over a computernetwork. In this case the request is made from one computer to anotherover, say, an ISDN network. The response is transmission of computerdata over the same ISDN network back to the first computer.)

FIG. 5 depicts a situation wherein a person involved in an automobileaccident requires prompt medical attention. The person makes the requestto the service operator using an existing communication network, e.g.,PSTN, cellular, etc. In one embodiment of the invention, allcommunication between the terminal unit and the service operator iscarried out via exchange of only data signals, i.e., without theexchange of voice or video signals. One advantage of communication usingdata-only signals is the low bandwidth requirement ofnon-audio/non-video signals.

The terminal unit attached to the calling person is similar to the onewhose block diagram appears in FIG. 4. Essentially, this terminal unitcontains within it a “location-calculator”, such as a GPS receiver, acommunication transceiver and a micro-computer. When the user triggers apanic call a specially coded message is transmitted from the terminaldevice to the service operator containing information such as theidentity code of the user and the terminal device, the nature of theemergency, the current location of the terminal device, and the time atwhich the call was triggered.

On receiving the request the service operator performs several actions,including, validation and authentication of the person requesting theservice, determining the nature of the emergency, determining if thecalling person has any special needs such as those relating to specifichealth conditions, determining the location of the calling person, anddetermining the most appropriate emergency response unit (ERU) tosummon. As depicted in FIG. 5 the service operator is connected to anentity called the Subscriber Management Element (SME), whose role is tostore and provide all the relevant information relating to thesubscriber, such as identification, password, address, credit history,billing status, etc.

Once the service operator determines the most appropriate ERU to call(based on, among other factors, the location of the calling person andany special needs they may have), it transmits a message to the ServiceDispatch Center (SDC) indicating all the relevant information pertainingto the subscriber and the particular emergency situation. Theresponsibility of the SDC is to call the ERU as directed by the serviceoperator.

In one embodiment of this system the service operator is completelyautomated, i.e., implemented without the involvement of any human beingin the processing of data. It is possible to implement the dispatchingof the ERU by the SDC using the dynamic addressing scheme described inthe first aspect of this invention although it is not necessary for thepurposes of the second aspect of this invention that the first aspect beused.

Establishing the initial contact with the ERU triggers the generation ofa first confirmation or acknowledgement signal from the SDC to theservice operator. This first confirmation is immediately relayed to thecalling person by the service operator. The purpose of the initialacknowledgement is to immediately notify the person in distress thathis/her request has been received by the appropriate response unit. Inone embodiment of the invention, the Expected Time of Arrival (ETA) ofthe ERU at the site of the accident is also presented to the person.

In the system architecture of FIG. 5, all messages between the terminalunit, the service operator, and the SDC are time-stamped. This means thetime of the original call, the actual time at which the ERU is firstnotified, as well as the time of the first acknowledgement, are allcaptured and logged in the system.

In most situations it is not possible for the ERU to instantaneouslyarrive at the location of the caller, even though the ERU may respondimmediately to the initial call. However, it could be beneficial for theoriginal caller to be made aware of the progress being made by the ERUtoward providing the requested service, e.g., how near the ERU is to thecaller, or how soon it is going to reach the caller. Depending on thesituation this information may be used by the caller to mitigate his/hercurrent exigency.

This invention extends the concept of the initial acknowledgement toinclude transmission of current status of the ERU to the original calleron a continual basis via the bi-directional communication network. Anaspect of this invention is that such status updates are providedautomatically without the intervention of any human being. For this tohappen the ERU has to be equipped with a device similar to that depictedin FIG. 4, i.e., a device that can compute its current geographicalcoordinates and communicate that to a remote device.

Again, referring to FIG. 5, once the SDC has established the initialcall with the ERU, it obtains all necessary parameters of the particularERU that are required to maintain communications with that ERU, inparticular the address of the terminal device attached to the ERU. Thisinformation is sent back to the service operator, upon the receipt ofwhich the service operator establishes a direct connection with the ERU.Once a connection is established the ERU can transfer informationregarding its current status to the service operator for further relayto the calling person. For example, the ETA of the ERU based on itscurrent location can be computed and relayed back to the calling person.Information may be uploaded from the ERU to the service operator eitherautomatically by the ERU (i.e., whenever it wants to), or it my beuploaded on-demand from the service operator (i.e., whenever it is askedto upload by the service operator). To those skilled in the art it iseasy to appreciate that either mechanism can be easily deployed, and itis a matter of implementation choice as to which one is actuallyemployed in a particular embodiment.

There are several possible configurations that enable the system tocapture and relay back to the calling person the status of the ERU. Thedifferent configurations trade-off the amount of intelligence residingin the terminal unit carried by the ERU and the service operator. FIG. 6depicts a table showing the trade-off between the ERU and the serviceoperator. In FIG. 6 the direction of increasing ERU terminal deviceintelligence corresponds to decreasing service operator intelligence,and vice versa. For example in the first row of the matrix, it is shownthat the terminal device in the ERU merely knows what its destination is(this would have been conveyed to it by the SDC). In contrast, theservice operator determines the location of the ERU using raw GPS datatransmitted to it by the ERU terminal device, computes the ETA at theemergency location, computes the requester's address value (i.e.,matches the incoming ERU message to the destination's address), andfinally transmits the information to the requester. At the otherextreme, as shown in the bottom row of the matrix in FIG. 6, all theabove steps are performed in the ERU itself, and the service operatormerely relays any information from the ERU to the requester. The othercases in FIG. 6 all fall between these two extremes. Which one of thedifferent configurations is deployed in a particular embodiment is amatter of implementation choice.

There are several methods for computing the ETA given the currentlocation of an entity and its intended destination location. One simplemechanism is to first compute the distance between the current point andthe destination point and divide the result by the average speed oftravel. The quotient obtained through the division added to the currenttime at the destination results in the ETA at the destination. Dependingon available information it may be possible to improve upon the ETAnumber by taking into account any real-life conditions, such asanticipated traffic delay during rush hour. Distance computation betweentwo points on the surface of the earth, given their latitude, longitudeand altitude is a well-researched topic, and many formulas for the sameexist in prior art.

FIG. 7 shows additional details of the terminal device depicted in FIG.4. In FIG. 7 the GPS subsystem captures and records the geographiclocation of the terminal unit. GPS stands for Global Positioning System,and is a system made freely available to the public by the USGovernment. A short description of the GPS system is given below;however, its operation is well known to those skilled in the art and canbe found easily in existing literature.

The GPS system consists of 24 satellite orbiting the earth at anapproximate height of 11,000 miles. Each satellite completes arevolution around the earth in about 12 hours. Signals transmitted bymultiple satellites are captured by the GPS subsystem and used todetermine its geographic co-ordinates.

The front-end of the GPS subsystem consists of an active antenna thatbandpass filters the satellite signals at a frequency of 1575.42 MHz,amplifies it using a Low Noise Amplifier (LNA) and feeds it to an RFdownconverter, which down-converts the incoming frequency and furtherfilters the signal before transferring it to an analog-to-digitalconvertor. The typical frequency of the signal at the output of the RFprocessor is 430 KHz. This signal processing is well known to thoseskilled in the art. The digitized signal leaving the analog-to-digitalconverter is subsequently decoded by a baseband processor. The basebandprocessor is typically a DSP chip with embedded firmware that isoptimized to handle the GPS signals, although other, more hardwarebased, implementations are also possible. Using information from 4satellites simultaneously, the GPS subsystem can accurately track thelongitude, latitude, altitude and velocity of the mobile unit.

The function of the communication subsystem in FIG. 7 is to provideconnectivity to the terminal unit with the communication network. Ingeneral, with reference to the system described in connection with FIG.5, the actual nature of the communication network is not important tothis invention, so long as this network supports basic, low bandwidth,bi-directional message passing.

In FIG. 7, the GSM digital cellular network is used as an example forthe communication network. GSM is a recently ratified global wirelessstandard, available in most of the world's nations. It supports a richand flexible messaging protocol called Short Message Service, or SMS,which can be used for the transferring the messages between therequesting entity, service operator, service dispatch center, andresponse unit of FIG. 5. Although GSM is used as an example of aparticular embodiment other wireless communication standards such asCDMA and TDMA can also be used in the context of FIG. 5. The portions ofthe terminal unit affected by the network technology relate to thecommunication subsystem; the overall functionality remains the same.

The GSM signal is transmitted around one of three frequencies dependingon the location of the network: 900 MHz, 1800 MHz, and 1900 MHz.However, the basic protocol structure and encoding technology is thesame in all cases. As in the GPS data path, the incoming analog RFfrequency is filtered, downconverted, digitized and decoded by the DSP.The firmware in the DSP extracts information retrieved from the incomingsignal and passes it to the microprocessor. The process for outgoingmessages is reversed.

The unit includes an RF transceiver, which performs the functions ofdecoding and encoding of data. There is no support for voice data in theterminal unit of FIG. 7. The host computer subsystem in FIG. 7 comprisesa simple microcontroller along with small amounts of volatile andnon-volatile memory. The microcontroller controls the GPS andcommunication subsystems as well as interacts with the user. Memory isrequired for storing both the resident application software as well asother data relating to the use of the terminal unit. The unit furtherincludes a Subscriber Interface Module (SIM), whose function is similarto the SIM modules used in GSM cellular phones, as is known to thoseskilled in the art. The user I/F represents the keypad, display andother interfaces required to communicate with the user.

FIG. 8 depicts the architecture of the service operator entity of FIG.5. As described above, the service operator is the “brains” of thesystem. It is the hub of the entire system, connecting to the terminalunit attached to the requester, the subscriber management element, theservice dispatch center, and the response unit. It performsauthentication and validation of the requesting entity based oninformation obtained from the subscriber management element, messagerouting, determination of location and type of service requested,directing the service dispatch center operator to the appropriateresponse unit, and returning service status information to therequesting entity. The service operator is preferably implemented toexecute as a fully redundant system with no single points of failures.

FIG. 8 depicts an embodiment of the service operator that presents anextremely modular design wherein the externally visible applications areseparated from the supporting hardware and software. Adistributed-modular architecture allows for system scaling withsubscriber growth. The specific embodiment of FIG. 8 depicts the serviceoperator as having several communication ports. The need for any ofthese ports is dependent on the implementation, and is typically thechoice of the system designer.

The lowest layer of the software consists of all the drivers and RAIDcontroller. The function of the RAID controller is to control the RAIDdatabase array that stores all the information relating to allsubscribers. The choice of RAID is for illustration purposes only;certainly other storage schemes could be employed. Just above the driverlayer in FIG. 8 sits the “middleware” portion of the service operator.The modules shown in the figure are merely for purposes of illustration;other modules could be required in certain other embodiments of theservice operator. The highest software layer is the ApplicationGraphical User Interface (GUI) that allows rapid and flexibledevelopment of applications.

The service dispatch center in FIG. 8 consists of fault-tolerantcomputers redundantly connected to the service operator. These computersare staffed by qualified operators who promptly respond to incomingmessages from the service operator by calling the appropriate responseunits. An initial acknowledgement is returned to the network server assoon as the appropriate response unit has been notified, as describedabove.

To maintain accurate logs of all transactions, every message isallocated a unique identity code, messages belonging to the same sessionare tagged to indicate the link between them, and every message is timeand date-stamped at the transmitting and receiving stations. Thefunction of the Subscriber Billing Computer in FIG. 8 is to maintain allthe financial records relating to the person requesting the service.This includes information such as level of service subscribed to, andcredit and payment history. The service operator interacts with theSubscriber Billing Computer to determine the level and quality ofservice to be provided to the requesting entity.

As described above the terminal device attached to the response unit cancome in several flavors, as depicted in FIG. 6. In one embodiment, theterminal unit uses the architecture depicted in FIG. 7; such a unit cancompute its location, and possibly even its ETA at the targetdestination. This information is uploaded to the service operatorwhenever the latter demands the data, as described above. Of courseother embodiments are possible as depicted in FIG. 6. However, in allembodiments the basic communication subsystem supports the transfer ofinformation between the response unit and the service operator.

References

The following references are incorporated by reference in their entiretyfor all purposes:

1. U. S. Pat. No. 5,633,913 to Talarmo, “Method for establishingconnection between communication devices.” May 27, 1997.

2. U. S. Pat. No. 5,604,921 to Alanara, “Radiotelephone user interfacefor broadcast short message service.” Feb. 18, 1997.

3. U. S. Pat. No. 4,878,051 to Andros et al., “Paging system withcommands for changing functionality of a paging receiver.” Oct. 31,1989.

4. U. S. Pat. No. 5,254,986 to DeLuca, “Nation-wide paging with localmodes of operation.” Oct. 19, 1993.

5. U. S. Pat. No. 5,519,403 to Bickley et al., “Global positioningsystem communications multi-interface.” May 21, 1996.

Conclusion

While the above is a complete description of specific embodiments of theinvention, various modifications, alternative constructions, andequivalents may be used. Therefore, the above description should not betaken as limiting the scope of the invention as defined by the claims.

What is claimed is:
 1. A system for dispatching a response unit inresponse to a request from a requesting entity, said system comprising:a terminal device attached to said requesting entity comprising at leasta location tracking device, a wireless communication device, and acomputer, said terminal device having the ability to uniquely identifyitself and its location over a wireless communication network to aremotely located service operator; a service operator connected to saidwireless communication network having attached to it relevantinformation relating to said requesting entity, said service operatorreceiving said request from said requesting entity; said serviceoperator interpreting said received request, authenticating saidrequesting entity and calling a service dispatch center with directionsto call a response unit, said response unit having attached to it aterminal unit having the ability to uniquely identify itself and itslocation to a remotely located service operator; said service dispatchcenter transmitting to said service operator a first acknowledgementmessage following first contact with said response unit, said firstacknowledgement message including a unique identifier code of saidresponse unit; said service operator transmitting back to saidrequesting entity said first acknowledgement message; said serviceoperator further initiating contact with said response unit anddetermining its location; and said system using said determined locationto compute an Expected Time of Arrival at the location of saidrequesting entity and transmitting said Expected Time of Arrival to saidrequesting entity.
 2. The system of claim 1 wherein: the servicedispatch center transmits a signal containing a message to the responseunit and a specification of a proximity constraint with respect to aspecific location; the response unit applies the proximity constraint tolocation information of the response unit; and the response unitresponds to the remotely located service operator only if theapplication of the proximity constraint by the response unit results ina true condition.
 3. The system of claim 1 wherein the wirelesscommunication network is a radiotelephone network.
 4. The system ofclaim 1 wherein the wireless communication network is a paging network.5. The system of claim 1 wherein the wireless communication network is abidirectional wireless communication network.
 6. The system of claim 1wherein: the response unit downloads a signal from the service dispatchcenter; the signal contains a proximity constraint with respect to aspecific location as well as a message; and the response unit appliesthe proximity constraint to location information of the response unitand uses the result of applying the proximity constraint to determine ifthe response unit is entitled to receive the message contained in thesignal.
 7. The system of claim 1 wherein: the service dispatch unitsends to the response unit a signal containing a message to becommunicated and at least one specific location; the response unit hasavailable location information for the response unit; and the responseunit responds to the remotely located service operator only if apredetermined proximity constraint is satisfied between the specificlocation and the location information for the response unit.
 8. Thesystem of claim 7 wherein the location information for the response unitis supplied to the-response unit by a global positioning system.
 9. Thesystem of claim 7 wherein the location information for the response unitis latitude and longitude coordinates.
 10. The system of claim 7 whereinthe signal contains data signals and does not include voice signals. 11.The system of claim 7 wherein the signal contains data signals and voicesignals.
 12. The system of claim 7 wherein the message contains medicalinformation of the requesting entity.
 13. The system of claim 1 whereinthe terminal unit attached to the response unit includes a locationtracking device.
 14. The system of claim 13 wherein the locationtracking device of the terminal unit attached to the response unit is aglobal positioning system receiver.
 15. The system of claim 1 whereinthe location tracking device of the terminal device attached to therequesting entity is a global positioning system receiver.
 16. Thesystem of claim 1 wherein the service operator is an automated system.17. The system of claim 1 wherein the service operator is operatedwithout human involvement.
 18. The system of claim 1 wherein saidresponse unit is configured to identify itself and its location over thewireless communication network to said remotely located serviceoperator.
 19. The system of claim 1 wherein said response unit isconfigured to identify itself and its location over a second wirelesscommunication network to said remotely located service operator.
 20. Thesystem of claim 1 wherein said response unit is configured to identifyitself and its location over the wireless communication network to saidremotely located service operator.
 21. The system of claim 1 whereinsaid response unit is configured to identify itself and its locationover a second communication network to the service dispatch center.